DC888A-B - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
LTC3725/LTC3706
DESCRIPTION
Demonstration circuit 888A-B is a high power isolated synchronous forward converter featuring the
LTC3725 and LTC3706. When powered from a 3672V input, a single DC888A-B provides an isolated
5V at 40A in a quarter-brick footprint. If higher output current is required, multiple DC888A boards may
be stacked together using on-board connectors for a
complete PolyPhase current sharing solution. The
converter operates at 250kHz and achieves efficiency
up to 93.5% with synchronous output rectifiers.
Secondary-side control eliminates complex optocou-
pler feedback, providing fast transient response with
a minimum amount of output capacitance. Additional
DC888A versions include DC888A-A (3.3V at 50A)
and DC888A-C (12V at 20A). The simple architecture
can be easily modified to meet different input and
output voltage requirements.
Design files for this circuit board are available.
Call the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Table 1. Performance Summary (TA = 25°C)
PARAMETER
CONDITION
VALUE
Minimum Input Voltage
36V
Maximum Input Voltage
72V
Output Voltage VOUT
VIN = 36V to 72V, IOUT = 0A to 40A
5V
Maximum Output Current
200LFM
40A
Typical Output Ripple VOUT
VIN = 48V, IOUT = 40A, 250kHz
< 60mVP–P
Output Regulation
Over All Input Voltages and Output Currents
±1% (Reference)
Peak Deviation with 20A to 40A Load Step (10A/us)
±250mV
Settling Time
•50us
Load Transient Response
Nominal Switching Frequency
250kHz
Efficiency
VIN = 36V, IOUT = 28A
93.5% Typical
Isolation
BASIC
1500VDC
Size
Component Area x Top x Bottom Component Height
2.3” x 1.45” x 0.4” x 0.075”
OPERATING PRINCIPLES – SINGLE PHASE
The LTC3706 secondary side controller is used on the
secondary and the LTC3725 smart driver with selfstarting capability is used on the primary. When an
input voltage is applied, the LTC3725 (U1 in Figure
15), which is powered through R29 and Q28, begins
a controlled soft-start of the output voltage by switching MOSFETs Q9 and Q11. As the output voltage begins to rise, the LTC3706 secondary controller is
quickly powered up via D24, Q29, C67, and Q27. The
LTC3706 then assumes control of the output voltage
by sending encoded PWM gate pulses to the
LTC3725 primary driver via signal transformer, T2.
The LTC3725 then operates as a simple driver receiving both input signals and bias power through T2.
The transition from primary to secondary control occurs seamlessly at a fraction of the output voltage.
From that point on, operation and design simplifies to
that of a simple buck converter. The LTC3706 regu-
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
lates by observing the output voltage directly resulting in superior output voltage regulation and transient
response.
OPERATING PRINCIPLES – POLYPHASE
The LTC3725 and LTC3706 allow the user to develop
modular power supply “building blocks” that can be
added as power/current requirements increase. Connecting two DC888A power supplies in a PolyPhase
configuration has several advantages. By distributing
power across multiple high power/current supplies,
heat is also distributed, reducing individual component temperatures. Each parallel module develops
equal output currents so that electrical and thermal
stresses are shared, increasing reliability. Multi-phase
operation and Shared input and output filtering result
in fewer/smaller input/output capacitors and inductors for a given voltage/current ripple or transient response.
In PolyPhase systems, one power supply is configured as a “master” and one as a “slave”. The master
communicates switching frequency via the PT+ pin to
FS/SYNC pin of the slave (Figures 19 and 20). The
relative clock phase of each stage is determined by
the slave. The master’s voltage error amplifier’s output (ITH pin) controls the output current of all the
phases via the ITH pin voltage which is distributed to
each slave’s unity-gain differential amplifier.
Several of the signals that are shared between the
master and the slave are of a bidirectional nature. A
fault on either phase can be communicated to the opposite phase via the primary side SS/FLT pin interconnection or the secondary side RUN/SS interconnection. Sharing Vcc on the secondary side ensures
the master, which initially develops this bias voltage,
and slave power up simultaneously. Each phase then
contributes to the shared Vcc bus. Finally, the input
voltage (Vin) and output voltage (Vout) busses are
interconnected to allow for load sharing.
OPTIONAL POLYPHASE SETUP
Only minor modifications and minimal interconnections are needed to implement PolyPhase with the
DC888. See component changes list (Figure 18) and
schematics (Figures 21 and 22) for the required electrical changes to master and slave units. After the
modifications are done, the boards are then stacked
one on top of another (Figure 23). J1 and P1 headers
interconnect small signals and E1, E2, E3, and E4
stand offs provide interconnection for the power signals.
The DC888 was designed primarily to demonstrate
the chipset’s single phase operation and therefore be
further optimized for PolyPhase applications. A small
resistor can be placed between the R76/D27 junction
and C70/U2-16 junction to reduce already small PWM
jitter associated with separate master and slave
ground planes. Another optimization can result from
combining each individual phase’s input/output filter
components into one shared input/output filter.
QUICK START PROCEDURE
Demonstration Circuit 888A-B is easy to set up to
evaluate the performance of the LTC3725 and
LTC3706. Refer to Figure 1 for proper equipment
setup. Follow the procedure below:
NOTE: When
measuring the input or output voltage
ripple, care must be taken to avoid a long ground lead
on the scope probe. Measure the output (or input)
voltage ripple by touching the probe tip and probe
2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
in order to measure the DC888A-B’s input current.
ground directly across the +Vout and –Vout (or +Vin
and –Vin) terminals. See 0 for proper scope probe
technique.
1.
The optional input LC filter stage (C2/L5) lowers ac
input rms current. A power supply’s complete input filter must have output impedance that is less
than the converter input impedance to assure stability. This may require a damping impedance. (See
Linear Technology Application Note AN19 for a
discussion of input filter stability.) A source with a
50mOhm or higher ESR at the filter resonant frequency is one way of providing damping for the filter elements provided on the DC888A. For bench
testing, adding an 82uF electrolytic capacitor such
as a Sanyo 100MV82AX to the input terminals will
provide suitable damping and ripple current capability. The values selected have a filter resonant
frequency that is below the converter switching
frequency, thus avoiding high circulating currents
in the filter.
2.
Set an input power supply to a voltage of 36V.
Make sure that it is capable of 36V to 72V at a current supplying capability of at least 8A per number
of phases being tested. Then, turn off the supply.
3.
With power off, connect the supply to the input
terminals +Vin and –Vin.
a.
b.
Input voltages lower than 36V can keep the converter from turning on due to the undervoltage
lockout feature of the LTC3725.
If efficiency measurements are desired, an ammeter capable of measuring at least 8Adc per
phase can be put in series with the input supply
c.
4.
A voltmeter with a capability of measuring • 72V
can be placed across the input to get an accurate
input voltage measurement.
Turn on the power at the input.
NOTE: Make sure that
the input voltage •72V.
5.
Check for the proper output voltage of 5V.
6.
Turn off the power at the input.
7.
Once the proper output voltages are established,
connect a variable load capable of sinking 40A per
phase at 5V to the output terminals +Vout and –
Vout. Set current to 0A.
8.
a.
If efficiency measurements are desired, an ammeter or a resistor current shunt that is capable
of handling at least 40Adc per phase can be put
in series with the output load in order to measure the DC888A-B’s output current.
b.
A voltmeter with a capability of measuring at
least 5V can be placed across the output terminals in order to get an accurate output voltage
measurement.
Turn on the power at the input.
NOTE: If
there is no output, disconnect the load to
verify that the load is not set too high.
9.
Once the proper output voltage is established, adjust the load within the operating range and observe the output voltage regulation, ripple voltage,
efficiency and other desired parameters.
3
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 1. Proper Measurement Equipment Setup
GND
VIN
Figure 2. Measuring Input or Output Ripple
4
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
MEASURED DATA
Figures 3 through 14 are measured data for a typical DC888A-B. Figures 15 through 23 consist of schematics, bill of
materials, and a picture.
Figure 3. Efficiency
Figure 4. Output Voltage Ripple (48Vin, 40A, Single Phase)
5
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 5. Load Transient Response (48Vin, 20A to 40A to 20A at 10A/us, Single Phase)
Figure 6. Loop Response (48Vin, 4A & 40A, Single Phase)
6
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 7. Turn-on (48Vin, 40A, Single Phase)
Figure 8. Turn-on (48Vin, 80A, PolyPhase)
7
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 9. Transient Sharing of Inductor Current (48Vin, 30A to 60A, PolyPhase)
Figure 10. Transient Sharing of Inductor Current (48Vin, 60A to 30A, PolyPhase)
8
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 11. Temp Data (48Vin, 40A, 200LFM airflow – top)
Figure 12. Temp Data (48Vin, 40A, 200LFM airflow – bottom)
9
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 13. Temp Data (48Vin, 36A, 0LFM airflow – top)
Figure 14. Temp Data (48Vin, 36A, 0LFM airflow – bottom)
10
B
A
T4
3
1
DA2318-ALC
6
4
D
C
D1
IS+
C29
10nF
SSFLT
U1
8.06
R76
1k
R84
3
+VOUT
C85
0.1uF
Q29
Si2303BDS
Vaux
FS/IN-
FB/IN+
LTC3725EMSE
R79
68K
D2
CMPSH1-4
100uH
L1
R29
100K
D27
BAS21
ULVO
VCC
C84
R80
0.1uF 100K
1uF
1nF
CMPSH1-4
D24
C24
2
1
8
Q28
FDC2512
C55
CMPSH1-4
R22
15.0K
R18
365K
NOTE:
C2-C5 2.2uF,100V Murata GRM32ER72A225K
L5 VISHAY IHLP2525CZERR68M01
T2 Pulse PA1954NL
-Vin
C3-C5
3 X 2.2uF
100V
3
C2
2.2uF
100V
7
36V-72Vin
4
10
5
4
100pF
C27
100
R3
5
6
4
3
1
2
750
SW
T2
1
8
B
C71
1uF
Q25
21
22
R53
12
R52
6.8
1/4W
FMMT718
Q14
Q15
Q24
C51
2.2n
100V
Si7336ADP
A
-VOUT
R51
6.8
1/4W
C69
2.2n
100V
11
10
8
7
-VOUT
Q30
2N7002
10pF
BAS21
R78
C83
D29
R63
100K
3
4
6
5
T1
PA0954(4:4:1:1)
C66
1.5n
200V
0.1uF
C101 C100
470pF 150pF
R101
100
5.1K
C72
R58
R48
15m
1.5W
Si7450DP
-VOUT Q8 Q9 Q11
T3
CT02-100
PT-
PT+
2.2nF
250V
C30
-VOUT
R23
VCC
-VOUT
3.3n
C70
-VOUT
D26
CMPSH1-4
SW
R75
510
C78
10nF
Vsg
IS+
SG
Si7336ADP
Q12
Q13
Q23
6.8 1/4W -VOUT
6.8 1/4W
R24
15
2
U2
LTC3706EGN
IS+
1
12
SG
R66
100K
150
C86
68pF
R82
R69
110K
L6
R81
100
R56
150
FCX491A
Q27
C67
10uF
25V
PA1382.650
Vaux
19
VIN
L5
2
FG
GND
20
SW
PGND
23
ISRUN/SS
8
NDRV
VSLMT
9
REGSD
17
100p
C75
24
C77
2.2uF
6
10
11
-VOUT
Q26
FMMT718
Vsg
Q32
FMMT619
VCC
FB
VS+
VS-
-VOUT
-VOUT
PSLV0J227M12
6.3V
220u
+ C31, C33, C68
+VOUT
VCC
C34
22n
Q31
MMBT2907A
C79
3.3n
R68
9.1K
VCC
0.68uH
13
GATE
PGND
6
PGOOD
3
16
SLP
14
1
SG
FS/SYNC
IS
GND
11
PHASE
5
18
NDRV
ITH
7
4
MODE
VSOUT
9
+Vin
R46
604
R41
4.42K
+Vout
-Vout
5Vo@40A
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 15. Single Phase Schematic
11
E2
1
P1-2
2
J1-2
2
P1-1
J1-1
6
4
T4
3
1
D
C
T4
6
4
C
Vout/Iout
3.3V@50A
5.0V@40A
12V@20A
VERSION
DC888A-B
DC888A-C
D1
C33
68uF, 16V
opt
220uF, 4V
220uF, 6.3V
C31,C68
1uF
1nF
2
1
8
SSFLT
C29
10nF
C34
10uF
22uF
C85
0.1uF
4.7nF
2.2nF
1.0nF
1.5nF
680pF
C51,C69
3
100pF
C27
C70
5
3.3nF
3.3nF
4.7uF 10nF
10uF
Vaux
FS/IN-
4
*
*
3
*
1
-VIN
R78
BAS21
D29
1
10pF
C83
11
10
8
7
T2
-VOUT
2.2nF
250V
C30
*
*
C71
-VOUT
*
36V
D31
C75
47pF
470pF
100pF
C79
4.7nF
4.7nF
3.3nF
BAS21
opt.
opt.
D30
MMBZ5258B
opt.
opt.
D31
L6
21
22
R53
12
Q25
4
PT-
PT+
*
PA1382.650
PA1494.242
R23
opt.
Q8
SG
* C70
VCC
-VOUT
D26
CMPSH1-4
SW
Si7450DP
U2
LTC3706EGN
Vaux
R67
opt.
2
4
5
*
*
opt.
Si7336ADP
10
6.8
5.1
Vsg
6
10
11
0.015
0.010
11.5K
0.015
R48
FB
VS+
VS-
*
+ C33
4.42K
2.74K
R41
Q26
FMMT718
-VOUT
*
C34
VCC
Q32
FMMT619
VCC
*
C79
*
R64
OPT
R68
Q23,Q24 R23,R24,R51,R52
R102
100
Q31
MMBT2907A
C75
*
3
1
2
FCX491A
Q27
25V
C67
*
L6
R56
150
R81
R69 R70
0
110K
VCC
Si7336ADP
Q12-Q15
150
C86
68pF
R82
R66
100K
HAT2244WP
C78
10nF
IS+
321
4
Vsg
*
SG
Q12
Q13
Q23
8765
1/4W -VOUT
R75
510
*
1/4W
*R24
Si7450DP
-VOUT
PA1382.650
1uF
321
8765
Q14
Q15
Q24
C51
*100V
FMMT718
1/4W
D30
1
8
B
R52
*
A
-VOUT
1/4W
R51
C69
*100V
SW
3
4
6
5
*
T1
Q30
2N7002
R63
100K
C82
opt.
C100
C101 150pF
470pF
R101
100
5
6
4
3
C66
200V
R48
1.5W
0.1uF
5.1K
C72
R58
123
5678
*
Q8
Q9 Q11
Si7450DP
1
2
NOTE:
C2-C5 2.2uF,100V Murata GRM32ER72A225K
L5 VISHAY IHLP2525CZERR68M01
T2 Pulse PA1954NL
opt.
C81
4
100
R3
0
R49
-VOUT
T3
CT02-100
FB/IN+
10uF
C67
+VOUT
C66
*
U1
Q29
Si2303BDS
1.5nF
*
2
R29
100K
* R76
* R84
3
LTC3725EMSE
R79
68K
D2
CMPSH1-4
R108
-VOUT
22uF
L1
100uH
R107
IS+
D27
BAS21
ULVO
C84
R80
0.1uF 100K
C24
3
VCC
C5
2.2uF
100V
Q28
FDC2512
C4
2.2uF
100V
C55
CMPSH1-4
D24
C3
2.2uF
100V
CMPSH1-4
R22
15.0K
* VERSION TABLE
D
DA2318-ALC
3
1
DC888A-A
B
A
T4 connection for A-A
B
A
T4 connection for A-B & A-C
SSP
-VIN
1
R18
365K
-VIN
TO CONFIGURE
FOR POLYPHASE
-Vin
C2
2.2uF
100V
6
5
2
1
4
4
10
IS
36V-72Vin
7
2
15
1
IS+
L5
12
19
VIN
3
9
2
FG
GND
20
SW
PGND
23
ISRUN/SS
8
NDRV
VSLMT
1
REGSD
17
18 1
0.68uH
13
GATE
PGND
6
GND
11
PGOOD
3
16
SLP
14
1
SG
FS/SYNC
24
VCC
E1
3
2
PHASE
5
NDRV
ITH
7
4
MODE
VSOUT
9
+Vin
6.2K
9.1K
9.1K
R68
C74
OPT
-VOUT
*
+ C31
+VOUT
*
620
750
390
7.50
R78
330
1.0K
2.2K
R84
-Vout
*
+Vout
C77
2.2uF
VCC
E4
8.06
9.53
R76
R46
604
OPT
R62
R41
*
E3
+ C68
E8
-
+
E7
R59
P1-4
opt.
240
opt.
R102
4
3
P1-3
OPT
R74
OPT
OPT
R72
R71
OPT
R60
OPT
R73
opt.
0
opt.
R107
4
3
0
opt.
0
T1
-VOUT
SSS
SYNC
-ITH
PA0955(6:6:2:1)
PA0954(4:4:1:1)
PA0950(6:6:1:1)
P1-11
11
J1-11
11
P1-10
10
J1-10
10
P1-9
9
J1-9
9
P1-8
8
J1-8
8
P1-7
7
J1-7 +ITH
7
+VPKS
R108
J1-4
J1-3
P1-6
-VOUT
OPT
P1-5
-VPKS
J1-5
J1-6
6
6
5
5
TO CONFIGURE
FOR POLYPHASE
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 16. Full Single Phase Schematic
12
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Qty
Reference
Part Description
Manufacturer / Part #
1
REQUIRED CIRCUIT COMPONENTS
3
C3,C4,C5
CAP., X7R, 2.2uF, 100V, 20%, 1210
2
C24,C71
CAP., X7R, 1.0uF, 16V 10%, 0805
1
C27,
CAP., C0G, 100pF, 50V, 10%, 0603
2
C29,C78
CAP., X7R, 10nF, 50V, 10%, 0603
1
C30
CAP., X7R, 2.2nF, 250V, 10%, 1812
3
C31,C33,C68
NeoCap., 220uF, 6.3V, 20%, V case
1
C34
CAP., X5R, 22uF, 6.3V, 20%, 1206
2
C51,C69
CAP., C0G, 2.2nF, 100V, 5%, 1206
1
C66
CAP., C0G, 1.5nF, 200V, 10%, 1206
1
C67
CAP., X7R, 10uF, 25V, 10%, 1210
1
C70
CAP., X7R, 3.3nF, 50V, 10%, 0603
1
C75
CAP., C0G, 100pF, 25V, 10%, 0603
1
C79
CAP., X7R, 3.3nF, 50V, 10%, 0603
1
C55
CAP., C0G, 1nF, 25V, 10%, 0603
1
C77
CAP., X7R, 2.2uF, 16V, 20%, 1206
1
C72
CAP., X7R, 0.1uF, 25V, 10%, 0805
1
C83
CAP., C0G, 10pF, 50V, 10%, 0603
2
C84,C85
CAP., X7R, 0.1uF, 50V, 10%, 0603
1
C86
CAP., C0G, 68pF, 25V, 10%, 0603
1
C100
CAP., C0G, 150pF, 25V, 10%, 0603
1
C101
CAP., C0G, 470pF, 25V, 10%, 0603
4
D1,D2,D24,D26
Diode Schottky, CMPSH1-4, 40V, SOT23
2
D27,D29
Diode, BAS21
SOT23
1
L1
INDUCTOR, 100uH, DO1606T
1
L6
INDUCTOR, PLANAR, 0.65uH
2
Q11,Q9,Q8
FET, N-CH., Si7450DP, Powerpak SO-8
6
Q12,Q13,Q14,Q15,Q23,Q24 FET, N-CH., Si7336ADP, Powerpak SO-8
2
Q25,Q26
TRANSISTOR, NPN, FMMT718, SOT23
1
Q27
TRANSISTOR, NPN, FCX491A, SOT89
1
Q28
FET, N-CH, FDC2512, SUPERSOT-6
1
Q29
FET, P-CH, 30-V(D-S) SOT-23
1
Q30
N-MOSFET, 2N7002 SOT23
1
Q31
TRANSISTOR, PNP, SOT-23
1
Q32
TRANSISTOR, NPN, SOT-23
3
R3,R56,R101
RES., CHIP, 100, 1/16W, 5%, 0603
1
R18
RES., CHIP, 365K, 1/8W, 1%, 0805
1
R22
RES., CHIP, 15.0K, 1/16W, 1%, 0603
4
R23,R24,R51,R52
RES., CHIP, 6.8, 1/4W, 5%, 1206
1
R41
RES., CHIP, 4.42K, 1/16W, 1%, 0603
1
R48
RES., CHIP, 0.015, 1.5W, 2%, 2512
1
RES., CHIP, 9.1K, 1/16W, 5%, 0603
R68
1
R76
RES., CHIP, 8.06, 1/16W, 1%, 0805
1
R78
RES., CHIP, 750, 1/16W, 5%, 0603
Murata, GRM32ER72A225K
TAIYO YUDEN, EMK212BJ105KG
AVX, 06035A101KAT2A
AVX, 06035C103KAT2A
Murata, GA343QR7GD222KW01L
NEC Tokin, TEPSLV0J227M(12)12R
TDK, C3216X5R0J226M
Murata, GRM3195C2A222JA01D
AVX, 12062A152KAT2A
Taiyo Yuden, TMK325BJ106KN
AVX, 06035C332KAT2A
AVX, 06033A101KAT2A
AVX, 06035C332KAT2A
AVX, 06033A102KAT2A
AVX, 1206YD225MAT2A
AVX, 08053C104KAT2A
AVX, 06035A100KAT2A
TDK, C1608X7R1H104K
AVX, 06033A680KAT2A
AVX, 06033A151KAT2A
AVX, 06033A471KAT2A
CENTRAL SEMI., CMPSH1-4-LTC
Diodes Inc., BAS21
Coilcraft, DO1606T-104MLC
PULSE, PA1382.650
VISHAY, Si7450DP
VISHAY, Si7336ADP-T1-e3
ZETEX, FMMT718
ZETEX, FCX491A
Fairchild, FDC2512_NL
VISHAY, Si2303BDS-T1-E3
Diodes Inc., 2N7002-7-F
DIODES., MMBT2907A-7-F
ZETEX, FMMT619
VISHAY, CRCW0603100RJNEA
VISHAY, CRCW0805365KFKEA
VISHAY, CRCW060315K0FKEA
VISHAY, CRCW12066R80JNEA
VISHAY, CRCW06034K42FKEA
IRC, LRC-LRF2512-01-R015-G
VISHAY, CRCW06039K10JNEA
VISHAY, CRCW08058R06FNEA
VISHAY, CRCW0603750RJNEA
13
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 17. Bill of Materials (Single Phase)
1
1
1
1
1
3
1
1
1
2
1
1
1
1
1
1
R84
R29
R46
R53
R58
R63,R66,R80
R69
R75
R79
R81,R82
T1
T2
T3
T4
U1
U2
RES., CHIP, 1.0K, 1/16W, 5%, 0805
RES., CHIP, 100K, 1/8W, 5%, 0805
RES., CHIP, 604, 1/16W, 1%, 0603
RES., CHIP, 12, 1/16W, 5%, 0603
RES., CHIP, 5.1K, 1/16W, 5%, 0603
RES., CHIP, 100K, 1/16W, 5%, 0603
RES., CHIP, 110K, 1/16W, 5%, 0603
RES., CHIP, 510, 1/16W, 5%, 0603
RES., CHIP, 68K, 1/8W, 5%, 0603
RES., CHIP, 150, 1/16W, 5%, 0603
TRANSFORMER, PLANAR, 4:4:1:1
TRANSFORMER, PA1954NL
TRANSFORMER, CT02-100
TRANSFORMER,
1.5 : 1
I.C. LTC3725EMSE, MS10E
I.C. LTC3706EGN, SSOP-24GN
VISHAY, CRCW08051K00JNEA
VISHAY, CRCW0805100KJNEA
VISHAY, CRCW0603604RFKEA
VISHAY, CRCW060312R0JNEA
VISHAY, CRCW06035K10JNEA
VISHAY, CRCW0603100KJNEA
VISHAY, CRCW0603110KJNEA
VISHAY, CRCW0603510RJNEA
VISHAY, CRCW060368K0JNEA
VISHAY, CRCW0603150RJNEA
PULSE, PA0954
PULSE, PA1954NL
ICE Components., CT02-100
Coilcraft, DA2318-ALC
LINEAR TECH., LTC3725EMSE#PBF
LINEAR TECH., LTC3706EGN#PBF
2
ADDITIONAL DEMO BOARD CIRCUIT COMPONENTS
1 C2
CAP., X7R, 2.2uF, 100V, 20%, 1210
0 C74(opt)
CAP.,
0603
0 C81,C82(opt.)
CAP.,
0603
0 D30 (opt)
Diode,
SOT23
0 D31 (opt)
Diode,
SOT23
1 L5
INDUCTOR, 0.68uH,
0 Q8(opt)
FET, N-CH., SO-8
2 R49,R70
RES., CHIP, 0, 1/16W, 0603
R59,R60.R62,R64,R67,R71
0
RES., 0603
-R74(opt)
RES., 0603
0 R102,R107(opt)
RES., CHIP, 0, 1/16W, 0603
1 R108
2 E1,E2
TESTPOINT, TURRET, .094"
2 E8,E7
TESTPOINT, TURRET, .061"
2 E3,E4
STUD
4 E3,E4(2 EACH)
NUT, BRASS, #10-32
2 E3,E4
WASHER, STAR #10 BRASS NICKEL
2 E3,E4
Ring, Lug Ring # 10
1 J1
HEADER, SMD, single row, 2mm
1 P1
SOCKET, SMD, single row, 2mm
Murata, GRM32ER72A225K
VISHAY, IHLP-2525CZERR68M01 e3
VISHAY, CRCW06030000Z0EA
VISHAY, CRCW06030000Z0EA
MILL-MAX, 2501-2-00-80-00-00-07-0
MILL-MAX, 2308-2-00-80-00-00-07-0
PEM, KFH-032-6
ANY
ANY
KEYSTONE 8205
Comm Com, 2SMD1-140/335/180-11G2
COMM COM, 1309-11G2
Notes:
1. Required Circuit Components are those parts that are required to implement the circuit function
2. Additional Demo Board Circuit Components are those parts that provide added functionality for the demo
board but are or may not be required in the actual circuit.
Figure 17. Bill of Materials (Single Phase) (cont’d)
14
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
SLAVE
MASTER
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Ref
Des
C29
C70
C78
R71
R72
R74
C29
C70
C78
C79
R41
R46
R59
R60
R62
R63
R64
R67
R68
R69
R70
R73
Single
Phase
10nF
3.3nF
10nF
OPT
OPT
OPT
10nF
3.3nF
10nF
3.3nF
4.42kΩ
604Ω
OPT
OPT
OPT
100kΩ
OPT
OPT
9.1kΩ
110kΩ
0Ω
OPT
PolyPhase
4.7nF
15nF
4.7nF
0Ω
0Ω
0Ω
4.7nF
15nF
4.7nF
open
open
open
0Ω
0Ω
0Ω
open
0Ω
0Ω
open
open
open
0Ω
Figure 18. Single Phase to PolyPhase Electrical Component Changes
15
1
1
2
1
P1-1
E2
E1
B
A
J1-2
6
4
2
T4
3
1
D
C
P1-2
DA2318-ALC
2
SSP (to SSP SLV)
1
-VIN (to SLV)
2
-Vin (to SLV)
J1-1
E2
E1
+Vin (to SLV)
D1
CMPSH1-4
D24
1nF
C55
CMPSH1-4
R22
15.0K
R18
365K
NOTE:
C2-C5 2.2uF,100V Murata GRM32ER72A225K
L5 VISHAY IHLP2525CZERR68M01
T2 Pulse PA1954NL
-Vin
C3-C5
3 X 2.2uF
100V
2
1
C29
4.7n
SSFLT
ULVO
VCC
R29
100K
U1
3
8.06
R76
1k
R84
4
+VOUT
C85
0.1uF
Q29
Si2303BDS
Vaux
FS/IN-
FB/IN+
LTC3725EMSE
R79
68K
D2
CMPSH1-4
100uH
L1
C84
R80
0.1uF 100K
1uF
C24
SSP
8
Q28
FDC2512
IS+
D27
BAS21
3
C2
2.2uF
100V
7
36V-72Vin
10
5
4
100pF
C27
100
R3
5
6
4
3
1
2
750
SW
T2
1
1uF
Q14
Q15
Q24
21
22
SYNC
R53
12
Q25
FMMT718
R52
6.8
1/4W
C71
8
B
C51
2.2n
100V
Si7336ADP
A
-VOUT
R51
6.8
1/4W
C69
2.2n
100V
11
10
8
7
-VOUT
Q30
2N7002
10pF
BAS21
R78
C83
D29
R63
100K
3
4
6
5
T1
PA0954(4:4:1:1)
C66
1.5n
200V
C101 C100
470pF 150pF
R101
100
0.1uF
5.1K
C72
R58
R48
15m
1.5W
Si7450DP
-VOUT Q8 Q9 Q11
T3
CT02-100
PT-
PT+
2.2nF
250V
C30
-VOUT
R23
VCC
15n
C70
-VOUT
D26
CMPSH1-4
SW
R75
510
-VOUT
C78
4.7nF
SSS
Vsg
IS+
SG
Si7336ADP
Q12
Q13
Q23
6.8 1/4W -VOUT
6.8 1/4W
R24
15
2
U2
LTC3706EGN
IS+
1
SG
R66
100K
150
C86
68pF
R82
R69
110K
L6
100
R56
150
R81
C79
3.3n
E3
E3
4
E4
E4
5
P1-5
6
Vsg
6
6
P1-6
7
7
P1-7
8
8
P1-8
9
9
P1-9
10
10
P1-10
J1-11
11
11
P1-11
-VOUT (to SLV)
J1-10
SSS (to SSS SLV)
J1-9
SYNC (to SYNC SLV)
J1-8
-ITH (to -ITH SLV)
J1-7
+ITH (to +ITH SLV)
J1-6
+VPKS (to +VPKS SLV)
5
-VPKS (to -VPKS SLV)
4
10
Q26
FMMT718
-VOUT
3
-Vout (to -Vout SLV)
3
+Vout (to +Vout SLV)
-Vout
J1-5
R46
604
R41
4.42K
+Vout
5Vo
11
Q32
FMMT619
VCC
FB
VS+
VS-
-VOUT
C77
2.2uF
PSLV0J227M12
6.3V
220u
+ C31, C33, C68
-VOUT
VCC
Q31
MMBT2907A
-ITH
100p
C75
R68
9.1K
+ITH
FCX491A
Q27
-VPKS
+VPKS
C67
10uF
25V
C34
22n
+VOUT
MASTER
PA1382.650
Vaux
19
VIN
L5
12
24
VCC
0.68uH
2
FG
GND
20
SW
PGND
23
ISRUN/SS
8
NDRV
VSLMT
9
REGSD
17
GATE
PGND
6
PGOOD
3
16
SLP
14
1
SG
FS/SYNC
13
IS
GND
11
PHASE
5
18
NDRV
ITH
7
4
MODE
VSOUT
9
+Vin
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 19. PolyPhase Master Schematic
16
1
1
2
1
P1-1
E2
E1
B
A
J1-2
6
4
2
T4
3
1
D
C
P1-2
DA2318-ALC
2
SSP (to SSP SLV)
1
-VIN (to SLV)
2
-Vin (to SLV)
J1-1
E2
E1
+Vin (to SLV)
D1
CMPSH1-4
D24
1nF
C55
CMPSH1-4
R22
15.0K
R18
365K
NOTE:
C2-C5 2.2uF,100V Murata GRM32ER72A225K
L5 VISHAY IHLP2525CZERR68M01
T2 Pulse PA1954NL
-Vin
C3-C5
3 X 2.2uF
100V
2
1
C29
4.7n
SSFLT
ULVO
VCC
R29
100K
U1
3
8.06
R76
1k
R84
4
+VOUT
C85
0.1uF
Q29
Si2303BDS
Vaux
FS/IN-
5
4
100pF
C27
100
R3
5
6
4
3
1
2
750
1
1uF
Q14
Q15
Q24
21
22
R53
12
Q25
FMMT718
R52
6.8
1/4W
C71
8
B
C51
2.2n
100V
Si7336ADP
A
-VOUT
R51
6.8
1/4W
C69
2.2n
100V
11
10
8
7
-VOUT
Q30
2N7002
10pF
BAS21
R78
C83
D29
T2
SW
3
4
6
5
T1
PA0954(4:4:1:1)
C66
1.5n
200V
C101 C100
470pF 150pF
R101
100
0.1uF
5.1K
C72
R58
R48
15m
1.5W
Si7450DP
-VOUT Q8 Q9 Q11
T3
CT02-100
FB/IN+
LTC3725EMSE
R79
68K
D2
CMPSH1-4
100uH
L1
C84
R80
0.1uF 100K
1uF
C24
SSP
8
Q28
FDC2512
IS+
D27
BAS21
3
C2
2.2uF
100V
7
PT-
PT+
2.2nF
250V
C30
-VOUT
R23
VCC
15n
C70
-VOUT
D26
CMPSH1-4
SW
R75
510
-VOUT
C78
4.7nF
SSS
Vsg
IS+
SG
Si7336ADP
Q12
Q13
Q23
6.8 1/4W -VOUT
15
36V-72Vin
10
6.8 1/4W
R24
U2
LTC3706EGN
IS+
2
12
SG
R66
100K
150
C86
68pF
R82
SYNC
L6
100
R56
150
R81
VCC
FCX491A
Q27
-VPKS
+VPKS
C67
10uF
25V
100p
C75
6
10
11
VCC
+ITH
Q26
FMMT718
Vsg
Q32
FMMT619
-VOUT
Q31
MMBT2907A
VCC
FB
VS+
VS-
-ITH
C77
2.2uF
-VOUT
-VOUT
PSLV0J227M12
6.3V
220u
+ C31, C33, C68
+VOUT
VCC
C34
22n
SLAVE
PA1382.650
Vaux
19
VIN
1
2
FG
GND
20
SW
PGND
23
ISRUN/SS
8
18
L5
3
16
SLP
NDRV
VSLMT
9
REGSD
17
24
VCC
0.68uH
13
GATE
PGND
6
PGOOD
14
1
SG
FS/SYNC
IS
GND
11
PHASE
5
NDRV
ITH
7
4
MODE
VSOUT
9
+Vin
+Vout
3
E3
E3
4
E4
E4
5
5
P1-5
6
6
P1-6
7
7
P1-7
8
8
P1-8
9
9
P1-9
10
10
P1-10
J1-11
11
11
P1-11
-VOUT (to SLV)
J1-10
SSS (to SSS SLV)
J1-9
SYNC (to SYNC SLV)
J1-8
-ITH (to -ITH SLV)
J1-7
+ITH (to +ITH SLV)
J1-6
+VPKS (to +VPKS SLV)
J1-5
-VPKS (to -VPKS SLV)
4
-Vout (to -Vout SLV)
3
+Vout (to +Vout SLV)
-Vout
5Vo
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 20. PolyPhase Slave Schematic
17
-VIN
1
6
4
T4
3
1
D
C
T4
6
4
Vout/Iout
3.3V@50A
5.0V@40A
12V@20A
VERSION
DC888A-B
DC888A-C
D1
C33
68uF, 16V
opt
220uF, 4V
220uF, 6.3V
C31,C68
3
2
1
8
15nF
10nF
2.2nF
1.0nF
1.5nF
22uF
10uF
680pF
4.7nF
15nF
C51,C69
C34
C66
C70
Vaux
1.5nF
*
+VOUT
3
FS/IN-
FB/IN+
100pF
C27
22uF
-VOUT
*
U1
*
R76
Q29
Si2303BDS
C85
0.1uF
D2
CMPSH1-4
R108
100uH
L1
2
R29
100K
3
* R84
4
LTC3725EMSE
R79
68K
4.7nF
SSFLT
C29
R107
IS+
ULVO
VCC
C84
R80
0.1uF 100K
1uF
1nF
CMPSH1-4
D24
C24
C55
CMPSH1-4
R22
15.0K
R18
365K
* VERSION TABLE
D
DA2318-ALC
3
1
DC888A-A
B
A
C
T4 connection for A-A
B
A
T4 connection for A-B & A-C
P1-2
2
J1-2
2
SSP (to SSP SLV)
P1-1
J1-1
1
-VIN (to SLV)
C5
2.2uF
100V
Q28
FDC2512
C4
2.2uF
100V
NOTE:
C2-C5 2.2uF,100V Murata GRM32ER72A225K
L5 VISHAY IHLP2525CZERR68M01
T2 Pulse PA1954NL
-Vin (to SLV)
E2
C3
2.2uF
100V
3
C2
2.2uF
100V
6
5
2
1
4
D27
BAS21
7
36V-72Vin
10
470pF
100pF
47pF
C75
5
opt.
C81
4
100
R3
0
R49
-VOUT
T3
CT02-100
4
4.7nF
3.3nF
*
1
1
10pF
C83
*
11
10
8
7
T2
-VOUT
*
*
C71
*
PA1382.650
PA1494.242
PA1382.650
-VOUT
36V
D31
21
22
R53
12
Q25
L6
1uF
321
8765
4
Q14
Q15
Q24
C51
*100V
FMMT718
1/4W
D30
1
8
B
R52
A
-VOUT
MMBZ5258B
opt.
opt.
D31
2.2nF
250V
C30
*
1/4W
R51
C69
*100V
SW
3
4
6
5
Q30
2N7002
BAS21
opt.
opt.
D30
-VIN
R78
BAS21
4.7nF
C79
3
D29
R63
100K
C82
opt.
C100
C101 150pF
470pF
R101
100
5
6
4
3
C66
*200V
* R48
1.5W
0.1uF
5.1K
C72
R58
123
5678
*
Q8
Q9 Q11
Si7450DP
1
2
T1
*
PT-
PT+
SG
Si7450DP
-VOUT
* C70
VCC
D26
CMPSH1-4
SW
C78
U2
LTC3706EGN
R82
R66
100K
100
opt.
Si7336ADP
HAT2244WP
150
R81
R56
opt.
R67
C75
*
R102
*
R41
4.42K
11.5K
10
2.74K
FB
VS+
0.010
0.015
0.015
6
6.2K
9.1K
9.1K
R68
10
11
*
+ C33
VS-
R48
Vsg
Q26
FMMT718
-VOUT
*
C34
VCC
Q32
FMMT619
VCC
*
C79
*
OPT
R68
R64
6.8
5.1
3
FCX491A
Q27
Q31
MMBT2907A
R69 R70
0
110K
VCC
2
1
2
C67
10uF
25V
*
L6
Q23,Q24 R23,R24,R51,R52
Si7336ADP
Q12-Q15
150
C86
68pF
4.7nF
IS+
321
4
Vaux
4
5
MASTER
Vsg
*
SG
Q12
Q13
Q23
8765
1/4W -VOUT
R75
510
*
Si7450DP
opt.
Q8
-VOUT
R23
1/4W
*R24
15
2
IS+
1
12
NDRV
9
2
FG
GND
20
SW
PGND
23
ISRUN/SS
8
16
SLP
19
VIN
L5
3
GATE
PGND
6
VSLMT
1
REGSD
17
18 1
0.68uH
13
IS
GND
11
PGOOD
14
1
SG
FS/SYNC
24
VCC
E1
3
2
PHASE
5
NDRV
ITH
7
4
MODE
VSOUT
9
+Vin (to SLV)
C74
OPT
7.50
8.06
9.53
R76
-VOUT
*
+ C31
+VOUT
*
390
620
750
R78
R46
604
OPT
R62
R41
*
E3
R84
330
1.0K
2.2K
opt.
240
R74
4
3
opt.
0
opt.
J1-6
J1-4
J1-3
opt.
0
0
R108
4
3
8
9
10
PA0955(6:6:2:1)
PA0954(4:4:1:1)
PA0950(6:6:1:1)
T1
-VOUT (to SLV)
P1-11
11
J1-11
11
P1-10
10
J1-10
SSS (to SSS SLV)
P1-9
9
J1-9
SYNC (to SYNC SLV)
P1-8
J1-8
8
-ITH (to -ITH SLV)
P1-7
7
7
J1-7
+ITH (to +ITH SLV)
+VPKS (to +VPKS SLV)
P1-5
-VPKS (to -VPKS SLV)
J1-5
P1-6
6
6
5
5
-VOUT
OPT
R107
P1-4
P1-3
0ohms
R102
opt.
R72
0ohms R73
0ohms
R71
OPT
R60
OPT
R59
-Vout (to -Vout SLV)
*
+Vout (to +Vout SLV)
C77
2.2uF
VCC
E4
+ C68
E8
-
+
E7
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 21. Full PolyPhase Master Schematic
18
E2
-VIN
1
1
6
4
T4
3
1
D
C
B
A
6
4
C
D1
Vout/Iout
3.3V@50A
5.0V@40A
12V@20A
VERSION
DC888A-A
DC888A-B
DC888A-C
68uF, 16V
SSFLT
C33
opt
100uH
L1
*
10uF
22uF
22uF
C34
*
2
R29
100K
U1
*
R76
* R84
3
1.0nF
4.7nF
2.2nF
680pF
C51,C69
C66
1.5nF
+VOUT
Vaux
FS/IN-
1.5nF
C85
0.1uF
3
Q29
Si2303BDS
100pF
C27
FB/IN+
LTC3725EMSE
R79
68K
4.7nF
C29
R107
IS+
D27
BAS21
ULVO
D2
CMPSH1-4
R108
-VOUT
220uF, 4V
220uF, 6.3V
C31,C68
2
1
8
C84
R80
0.1uF 100K
1uF
1nF
CMPSH1-4
D24
C24
3
VCC
C5
2.2uF
100V
Q28
FDC2512
C4
2.2uF
100V
C55
CMPSH1-4
R22
15.0K
R18
365K
* VERSION TABLE
D
DA2318-ALC
3
1
T4
T4 connection for A-A
B
A
T4 connection for A-B & A-C
P1-2
2
J1-2
SSP (to SSP MSTR) 2
P1-1
J1-1
-VIN (to MSTR)
NOTE:
C2-C5 2.2uF,100V Murata GRM32ER72A225K
L5 VISHAY IHLP2525CZERR68M01
T2 Pulse PA1954NL
-Vin (to MSTR)
C3
2.2uF
100V
6
5
2
1
4
C2
2.2uF
100V
3
36V-72Vin
7
4
10
10nF
15nF
15nF
C70
5
opt.
C81
4
100
R3
0
R49
-VOUT
T3
CT02-100
4
*
470pF
*
1
1
10pF
C83
*
11
10
8
7
T2
-VOUT
*
*
C71
*
PA1382.650
PA1494.242
PA1382.650
-VOUT
36V
D31
21
22
R53
12
Q25
L6
1uF
321
8765
4
Q14
Q15
Q24
C51
*100V
FMMT718
1/4W
D30
1
8
B
R52
A
-VOUT
MMBZ5258B
opt.
opt.
D31
2.2nF
250V
C30
*
1/4W
R51
C69
*100V
SW
3
4
6
5
Q30
2N7002
BAS21
opt.
opt.
D30
-VIN
R78
BAS21
100pF
47pF
C75
3
D29
R63
100K
C82
opt.
C100
C101 150pF
470pF
R101
100
5
6
4
3
C66
*200V
R48
1.5W
0.1uF
5.1K
C72
R58
123
5678
*
Q8
Q9 Q11
Si7450DP
1
2
T1
*
PT-
PT+
SG
Si7450DP
* C70
VCC
-VOUT
D26
CMPSH1-4
SW
C78
U2
LTC3706EGN
150
C86
68pF
R82
R66
100K
HAT2244WP
150
R56
VCC
*
R102
opt.
10
6.8
5.1
*
Q26
FMMT718
R48
8.06
7.50
0.010
9.53
0.015
0.015
FB
R76
Vsg
Q32
FMMT619
-VOUT
Q31
MMBT2907A
C79
*
VS-
6
390
620
750
R78
10
11
*
+ C33
VS+
VCC
*
C34
0ohms
R64
R68
C75
*
3
FCX491A
Q27
1
2
0ohms
R67
2
*
25V
C67
*
L6
R69 R70
0
110K
VCC
R81
100
Vaux
4
5
SLAVE
Q23,Q24 R23,R24,R51,R52
Si7336ADP
Si7336ADP
Q12-Q15
4.7nF
IS+
321
4
Vsg
*
SG
Q12
Q13
Q23
8765
1/4W -VOUT
R75
510
*
Si7450DP
opt.
Q8
-VOUT
R23
1/4W
*R24
15
2
IS+
1
19
VIN
L5
12
NDRV
9
VSLMT
1
2
FG
GND
20
SW
PGND
23
ISRUN/SS
8
GATE
PGND
6
REGSD
17
18 1
0.68uH
13
IS
GND
11
PGOOD
3
16
SLP
14
1
SG
FS/SYNC
24
VCC
E1
3
2
PHASE
5
NDRV
ITH
7
4
MODE
VSOUT
9
+Vin (to MSTR)
C74
OPT
330
1.0K
2.2K
R84
-VOUT
*
+ C31
+VOUT
*
opt.
240
opt.
R102
R46
604
E4
opt.
0
opt.
R107
opt.
0
0
R108
0ohms
R73
4
3
T1
4
3
-VOUT
8
P1-9
9
J1-9
9
P1-8
J1-8
8
-ITH (to -ITH MSTR)
P1-7
7
7
J1-7
+ITH (to +ITH MSTR)
J1-4
J1-3
PA0955(6:6:2:1)
PA0954(4:4:1:1)
11
P1-11
11
J1-11
-VOUT (to MSTR)
P1-10
10
10
J1-10
SSS (to SSS MSTR)
SYNC (to SYNC MSTR)
P1-6
6
+VPKS (to +VPKS MSTR)
P1-5
J1-5
-VPKS (to -VPKS MSTR)
J1-6
6
5
5
PA0950(6:6:1:1)
P1-4
P1-3
OPT
R74
OPT
OPT
R72
R71
0ohms
R60
0ohms
R59
-Vout (to -Vout MSTR)
*
+Vout (to +Vout MSTR)
C77
2.2uF
VCC
0ohms
R62
R41
*
E3
+ C68
E8
-
+
E7
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 22. Full PolyPhase Slave Schematic
19
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 888A-B
36V-72VIN, ISOLATED SYNCHRONOUS FORWARD
Figure 23. Picture of two DC888A’s configured for PolyPhase
20